<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    #tutorial1 {
        width: 500px;
        height: 500px;
        /* background-color: aqua; */
        margin: 150px auto;
        border: 1px solid black;
    }
</style>
<body>
    <div id="tutorial1"></div>
</body>
<script>
    var ctx;
    function draw() {
        var canvas = document.getElementById('tutorial1');
        if (!canvas.getContext) return;
        var ctx = canvas.getContext("2d");

        ctx.beginPath();
        ctx.arc(20, 20, 100, 0, Math.PI * 2);
        ctx.clip();

        ctx.fillStyle = "pink";
        ctx.fillRect(20, 20, 100, 100);
    }
    draw();
</script>

</html>